pe.header: added ability to parse part of pe header without dos

src/pe/header.rs

@@ -543,14 +543,15 @@ pub struct Header {
 }
 
 impl Header {
+    /// Parses PE header from the given bytes, use default DosHeader if missed
     pub fn parse(bytes: &[u8]) -> error::Result<Self> {
-        let dos_header = DosHeader::parse(&bytes)?;
+        let dos_header = DosHeader::parse(&bytes).unwrap_or_default();
         let dos_stub = bytes.pread(DOS_STUB_OFFSET as usize).map_err(|_| {
             error::Error::Malformed(format!(
                 "cannot parse DOS stub (offset {:#x})",
                 DOS_STUB_OFFSET
             ))
-        })?;
+        }).unwrap_or_default();
         let mut offset = dos_header.pe_pointer as usize;
         let signature = bytes.gread_with(&mut offset, scroll::LE).map_err(|_| {
             error::Error::Malformed(format!("cannot parse PE signature (offset {:#x})", offset))